The 21× Multiplier: What It Costs to Compute a Delta

mail@carlosprados.com (Carlos Prados) — Thu, 20 Aug 2026 00:00:00 +0000

Everyone measures the patch. On the two binaries in this post, a delta replaces a 13.6 MB download with a 250 KB one — and that ratio is the whole pitch. On NB-IoT at 20 kbps it is the difference between an hour and a half and under two minutes.

Nobody measures what it costs to make the patch.

For a 13.6 MB Go binary, bsdiff peaks at 296 MiB of resident memory. Not a leak, not a bug: that is the algorithm’s working set, allocated and released for every patch you generate. Twenty-one times the input.

The 2% Delta: Why Your Differential Updates Save Nothing

mail@carlosprados.com (Carlos Prados) — Thu, 13 Aug 2026 00:00:00 +0000

Here’s the pitch every OTA system makes: don’t ship the whole binary, ship the difference. You changed three functions, so send three functions’ worth of bytes. On a fleet connected over NB-IoT at 20–60 kbps, that is the difference between an update that lands and an update that times out for two hours.

I wanted that for Keystone, my edge orchestration agent. So before building anything, I measured it against two real consecutive releases.

Go on EnRedAndo Me - Carlos Prados

The 21× Multiplier: What It Costs to Compute a Delta

The 2% Delta: Why Your Differential Updates Save Nothing